The aim of the talk is to explain an unexpected link between a class of molecules composed of carbon and hydrogen atoms, and the theory of elliptic curves over finite fields. The correspondence is of topological nature and doesn't include, so far, any of the crucial geometric features of the cycloalkanes. We will nevertheless explain how modular curves help making this connection, the role of modular polynomials, give details about explicit computations we performed, and give several examples. The talk is based on joint work with Henry Bambury and Francesco Campagna.